Robotics and Automation in Construction 2012 Part 10 doc

The exhibit contained the movable monument was built on the roof of the house.The entire exhibit was composed of movable towers and an annexed device of a Karakuri doll.. Development of

Development of Adaptive Construction Structure by Variable Geometry Truss 263

4 Develpment of a movable monument applying VGT mechanism exhibited

in Expo 2005

AS for the other practical example applying VGT mechanism, Development of a movable monument is mentioned in this paragraph

4.1 Outline of a movable monument

4.1.1 Background and outline of the development

Expo 2005 in Aichi, Japan ended successfully about 3 year ago, with more than two million people attending from around the world There were various exhibitions, entertainments, attractive buildings, new technology and events based on the theme of “Nature’s wisdom” One remarkable technology displayed at the Expo was the application and performance of automated robots For example, music-playing robots in a group, automatic cleaning robots, guard robots, etc These scenes might be imagined a the future and such technologies continue to be developed

In the Japanese zone of the Aichi prefecture pavilion near the center of the exhibition as showing in Fig.15, there was a large monument in the shape of a traditional Karakuri doll beckoning visitors inside The exhibit here was called “Dancing Tower with Karakuri doll Performance”, and was exhibited as a symbol of Aichi district’s culture, harmonizing traditional technology with revolutionary new ones

Fig 15 Overall Map of Expo Site and Nagakute Aichi Prefecture Pavilion exhibited Movable

Monument (From the Expo 2005 Pamphlet of Aichi Prefecture in Japan)

For the Nagakute Aichi prefecture pavilion, the Expo organizers requested a design for a monument comprising a symbol tower to attract visitors to the pavilion We proposed a movable monument whose shape could be changed variably and irregularly A large movable monument using VGT was selected as a very unique and attractive monument

A picture of the Expo site and the Nagakute Aichi Prefecture pavilion where the movable monument was set up is shown in Fig.15, and the movable monument is outlined in Table 1 The pavilion was in a picturesque position in the Japanese zone at the center of the Expo site It faced a Japanese garden and the Kaede pond It was located in front of the west gate and beside a global loop, making visitor access easy The pavilion consisted of a festival plaza, a large-scale theater and a stage, a large area of the Cyube exchange pavilion, and an administration building The exhibit contained the movable monument was built on the roof

of the house.The entire exhibit was composed of movable towers and an annexed device of a Karakuri doll Each exhibit was united by an internal control signal, and various performances by both the monument and the Karakuri doll were planned

Table 1 Outline of Movable Monument

4.1.2 Design of movable monument

Fig.16 shows schematic pictures of the entire movable monument and its base structure The whole was composed of three movable iron towers of the same specification, and were spaced at 120-degree intervals around the circumference Each tower comprised four truss members combined by VGT at joints Each frame comprised a solid truss structure The outside of the frame was equipped with a hinge, the inside combined slide actuator, and the shape of towers was changed in proportion to actuator length Moreover, head illumination was provided at the point of the monument, and a artistic lightning rod was set up A Karakuri device covered with a large lantern case was constructed at the center of the monument The towers were seated on a base plate and were combined with long steelpaling that penetrated through the inside of the administration building to an anchor

4.1.3 Structure design

In the movable structure’s design, it was necessary to ensure adequate security Then, the evaluation of the structure’s design and its performance was acquired from the designated organizations For design, the earthquake force for a projection on the rooftop and the wind loading based on the regional average wind velocity were used A section shape was selected to ensure security and the specification of the VGT actuator was decided Moreover, the control system for the movable mechanism, the safety mechanism, the management and the operation system were examined and approved

Development of Adaptive Construction Structure by Variable Geometry Truss 265

Solid Truss

VGT Actuator

Karakuri doll device

Solid Truss

VGT Actuator

Karakuri doll device

Fig 16 Schematic Pictures of a Movable Monument and Base Structure

4.2 Composition of movable monument and control system

4.2.1 VGT actuator and monument structure

Fig.17 shows the arrangement of the VGT actuator and the movable range of the tower Three different sized VGT actuators were set up in each tower and were controlled independently There were two VGT mechanism arrangements: pier type and chord type In this tower, the chord type arrangement was adopted because it had advantages of higher rigidity, higher accuracy and lower actuator load The rotation angle of the VGT mechanism was from 2.5 degrees inside to 18 degrees outside Thus, the total maximum rotation angle

of a tower equipped with three VGT mechanisms was from 7.5 degrees inside to 54 degrees outside

Top iIluminations

Limit of outer angleLimit of

inner angle

Max circularvelocity:

Top iIluminations

Limit of outer angleLimit of

inner angle

Max circularvelocity:

Fig.18 shows a picture of the inner structure of an extensible actuator used in a VGT Mechanism The actuator was of the electronic type in which a screw rod was geared to a servomotor through a ball screw and a wheel gear The top of the screw rod was linked with

a truss node and the body of the actuator was carried by trunnion joints The support bars

on the node were moved in the outer stopper Even if the screw rod broke, the tower’s safety could be maintained by the support bars In the servomotor, a magnetic brake and an encoder detect the rotating angle

On the rod cover, both top and end limit sensors were installed The motor was covered with waterproof covers A cooling fan was maintained a suitable motor temperature The electronic actuator had the advantage of high performance and energy conservation

① Stroke Control by Encoder

②End limit Sensor

③ Released Stopper

Trunnion Joint

④ Limit of Inner Stopper

⑤ Limit of Outer Stopper

Inner Stopper

Outer StopperHinge

Screw Rod Servo-motor

①Normal Stroke Range

②End Sensor Range

③Released Stopper Clash Range

④Inner Stopper Range

⑤Outer Stopper Range

① Stroke Control by Encoder

②End limit Sensor

③ Released Stopper

Trunnion Joint

④ Limit of Inner Stopper

⑤ Limit of Outer Stopper

Inner Stopper

Outer StopperHinge

Screw Rod

Servo-motor

① Stroke Control by Encoder

②End limit Sensor

③ Released Stopper

Trunnion Joint

④ Limit of Inner Stopper

⑤ Limit of Outer Stopper

Inner Stopper

Outer StopperHinge

Screw Rod Servo-motor

①Normal Stroke Range

②End Sensor Range

③Released Stopper Clash Range

④Inner Stopper Range

⑤Outer Stopper Range

①Normal Stroke Range

②End Sensor Range

③Released Stopper Clash Range

④Inner Stopper Range

⑤Outer Stopper Range

Fig 18 Inner Structure of the Extensible Actuator of VGT and Safe Mechanisms

The relation between the load acting on the rod and the angle of each VGT mechanism are indicated in Fig.19 when the tower’s movement analyzed by numerical simulation at the same angle The load values were almost proportional to the angle, and the tension force range was wide and high The rod’s peak velocity was 20 mm/s, the tower tip rotation velocity became 500 mm/s or more when three VGT were operating at the same time The tower movement could be expressed in an extremely dynamic and massive way in comparison with a conventional monument

Development of Adaptive Construction Structure by Variable Geometry Truss 267

Fig 19 Relation between Load Acting on Rod and Angle of each VGT Mechanism

4.2.2 Safety mechanism and control system

The movable monument used at the Expo had to operate continuously, so a safe structure and control system had to be developed The actuator rod stroke was detected by the servomotor encoder data and the actuator condition was continually monitored Various accidents to the monuments were assumed, and the check points and safety mechanisms indicated were introduced For an accident concerning rod stroke, a five-step safety mechanism was introduced

Fig.20 shows a chart of the operation system and plural fail-safe system Monument operation was automated, except the initial process, and the operator mainly observed the system’s safety confirmation and maintenance control The plural fail-safe system that maintained monument safety was developed to avoid accidents Furthermore, an emergency device; an automatic stop and warning device for earthquakes, thunderstorms, strong winds and heavy rain; and a backup device for power failure were installed

Fig 20 Flowchart of Operation System and Monument Safety System

4.3 Performance and operation conditions of movable monument

An overview of the movable monument at Expo is shown in Fig.21 This picture expresses the coordinated performance of the three towers of the monument when fully opened (Fig.21-(a)), and Karakuri doll dancing in the center (Fig.21-(b)) A lot of visitors gathered around the monument, and they enjoyed the performance of the two exhibitions Further, the monument was illuminated at night and its fantastic movements could be observed in the dark (Fig.21-(c))

(a) Performance of the Three Towers of the Monument When Fully Opened

(b) Karakuri Doll Performance (c)Lightening up the Monumnt

Fig 21 Overview of the Movable Monument at EXPO

4.3.1 Performance patterns and shape change

Fig.22 shows the monument’s shape changes according to performance patterns One loop

of the total performance was composed of two patterns every 30 minutes, that is, only the monument was moved for the 25 minutes of the first part, and the Karakuri doll danced with the monument for the 5 minutes of the second part This performance loop was continuously repeated

Development of Adaptive Construction Structure by Variable Geometry Truss 269 For the monument’s performance, there were two program modes In the normal mode, the velocity and the stopping time of the actuator rod were decided by measuring and indicated

in Fig.22-(a) There was a little case in which the shape of three towers reappeared at the same time In a special mode, the monument was moved at high speed to accompany analyzing the state of the natural data (wind velocity, temperature, time, day and so on) As

a result, the entire monument was moved to produce very irregular shape changes, as a preinstall program This mode, being outside the performance loop, started suddenly, so nobody was expecting it By selecting such modes, it was possible to express very interesting movements and monument shapes that changed slowly but dynamically

(a) Random Shape Performance of the Monument by Natural Data (25 min.)

(b) Harmonized Performance of the Karakuri and the Monument (5 min.)

Fig 22 Shape Changes of Monument According to Performance Patterns

On the other hand, in the coordinated performance with the Karakuri doll, the monument was opened and closed powerfully, synchronizing with the Karakuri doll’s performance, as indicated in Fig.2-(b) In this case, the Karakuri doll performed a variable dance and somersaults with sound and illumination effect A very traditional but innovative performance was thus created In this performance, the Karakuri doll was the main player and the monument was a supporting player

4.3.2 Monument operation

During the Expo, the monument was operated continuously for about 13 hours a day However, its operation was modified every day and at times when there were unexpected special events Fig.23 shows the record of operation frequency each day and their accumulations When the shape of the monument was changed to open and to close, the operation was counted as one

Fig 23 Record of Monument’s Operation Frequency during the Expo

At the beginning of the Expo, the average speed at which the monument moved was set at a low level, and the speed was changed depending on the day of the week Two months after opening, the performance was switched to a random mode program The operation frequency was observed to be almost constant During the last month, the average speed approached the maximum level corresponding to the upsurge in attendance at the Expo site During the Expo, the monument was operated continuously for 185 days, except during

Development of Adaptive Construction Structure by Variable Geometry Truss 271 maintenance or thunderstorms, and there were neither breakdowns nor accidents By the end of the Expo, there had been 50,000 operations, thus confirming that the monument wasoperated within the range of the initial plan

After the Expo ended, the monument and other devices were temporarily removed from the site In response to demands for its reconstruction, it was reconstructed in the field of the company that manufactured the VGT actuator, and is now open to the public as a memorial tower to the Expo It may continue operating forever

5 Conclusion

As for one movable mechanism that enables to make a future adaptive structure, we focused the VGT, and examined the development of element technolgies and its applicability to moveable structures VGT was equipped with flexible and intelligent functions, and various shapes could be created freely by contriving its arrangement and control The structure was considered to have a very wide application to construction sturucture This paper has proposed an example of an adaptive structure applying the VGT The efficiency and the characteristics of the VGT could be grasped under the several conditions by a scale model of

a Flowering Dome and a movable monument exhibited in EXPO Application of the movable monumnet was the first big project since the VGT technology had been developed

in the construction field In the development of the monument, we considered quality and security of construction As a result, safe and excellent continuous performance was achieved, and the monument received high praise from promoters and many visitors The VGT was shown to be a very useful technology for such movable structures whose shape can be changed variably In the future, with progressing and spreading of VGT technology,

we will propose various applications

Finally, the author thanks all who supported the development and application of the VGT structure and a movable monument at Expo 2005

6 References

Ishii, K (1995) Moving Architectures Journal of Architecture and Building Science, Vol 110,

No 3, pp 3-44

Natori, M.C., & Miura, K (1994) Development of truss concept in Space Technology

International Symposium on Membrane Structure and Space Frame, pp 45-56

Kurita, K., Inoue, F., Natori, M C et al (2001) Development of Adaptive Roof Structure by

Variable Geometry Truss Proceeding of 18th International, Symposium on Automation and Robotics in Construction , pp.63-68, Sep 2001, Krakow, Poland

Inoue, F., Kurita, K.et al (2003) Application of Adaptive Structure And Control by Variable

Geometry Truss Proceeding of The CIB 2003 International Conference on Smart and Sustainable Built Environment, pp.59, Nov 2003, Brisbane, Australia

Inoue, F., Kurita,K et al (2006) Development of Adaptive Structure by Variable Geometry

Truss Proceeding of 23th International Symposium on Automation and Robotics in Construction, pp.704-709, Oct 2006, Tokyo, Japan

Inoue, F (2007) A Study of Movable Arch Strycture and its External Panel Mechanism by

Variable Geometry Truss International Conference of Shell and Spatial Structures,

pp.704-709, Dec 2007, Venice Italy

1.1 Introduction

Excavation in general term is the process of removing soil, ore or any bulk material from its original place, by digging out or digging away, and loading it (say, onto a vehicle for hauling) In this sense, it covers a variety of methods that may or may not include all the different functions of loosening (or cutting) the material, digging it and finally loading it Also, the equipment used for this purpose are different, based on the geometry and physical properties of the environment they excavate, and the way the three basic functions (loosening, digging and loading) are executed (sequentially or combined together) There are two types of machines, in general, rotary and cyclic The work here is intended for automation of cyclic excavating machines

Automation of excavation process becomes required in a number of applications For instance, in mining for more productivity, safety of workers and more efficiency an automated system is desirable; in remote places like moon an automated excavating device

is required to get samples Hazardous contaminated soil removing and mining radioactive materials are other examples

Attention must be paid to the difference between an excavation operation and an excavation process The latter is the function performed by an excavator Thus, excavation process comprises a combination of cutting, digging and scooping Automation of the process, in fact, implies the automation of the machine that performs the task For automation, an analysis of the process and what is involved in it is necessary

It is very important to note that the physical properties of the material to be excavated have

a direct effect on the excavation method and the properties and design of the equipment In fact they significantly determine the forces required on the cutting tool, and hence the power requirement of the machine For simplicity of expression, hereafter, the material to be excavated will be referred to as “bulk media” or "soil" Also, instead of excavation automaton, the term “robotic excavation” is often interchangeably used

1.2 Chapter contents

A general but brief review of the various excavation processes and the sort of machines in use is given in section 2 This will indicate the broad scope of the scenarios on excavation and its automation The emphasis of the chapter is to make a distinction between what is involved in an excavation operation and the process of excavation, itself In section 3 the question of automating the excavation operation is investigated An example illustrates all the various tasks to be automated in an excavation operation by a particular class of an excavating machine In this work, we narrow down our concern only to the issues relevant directly to automating an excavation process Section 4 covers the analysis of the forces involved in an excavation process These force components vary during the excavation and depend on the machine used These are the forces that the cutting tool of an excavator must overcome Knowledge about the force of excavation is quite important to automation of the task Section 5 covers the analysis of robotic excavation and the necessary steps to be followed for robotic modelling of an excavating machine The discussion is enhanced by some detailed analysis of a front-end loader and its counter part in underground mining (Hemami, 1992) This example is used for all the other discussions throughout the chapter Section 6 is devoted to modelling of a front-end-loader type excavator as a robot manipulator Section 7 considers the nature of what happens in an excavation process and how it can be modelled The criteria to be used for automating such a process are also discussed Section 8 elaborates on the conclusion of what must be carried out towards a workable automated machine

2 Excavation methods and equipment

2.1 General excavation methods

Although not a sharp distinction line could, in general, be drawn between the various types

of excavation, but because of dependency of the scope of operation on the factors such as: the quantity of the soil to be moved, the location of the excavation site, the relative width, breadth and depth, the type of soil and the purpose of excavation, excavation falls into the following basic types:

1 bulk-pit excavation

2 bulk wide area excavation

3 loose bulk excavation

4 limited-area vertical excavation

5 trench excavation

6 tunnel excavation

7 dredging

Bulk-pit excavation is excavation of considerable depth as well as considerable volume The

equipment must work against the face of nearly vertical walls from inside the pit, and the soil must be hauled away

Bulk wide-area excavation is like the bulk-pit excavation, but shallower in depth and larger

in area, and the site is accessible from many directions The excavated soil is hauled a shorter distance

Loose bulk excavation is like excavation of canals where the soil is not hauled away but cast

into a new position Moreover, the operation is usually performed from the surrounding ground rather than from inside the pit

Robotic Excavation 275

Limited-area vertical excavation is where the soil must, out of necessity, be lifted out

vertically; the method is used for loose and wet soil, and the banks must be supported by shoring or sheathing

Trench excavation sometimes falls into the category of the limited- area vertical excavation;

generally, the width and depth of operation are limited

Tunnel excavation is completely underground; the width and depth (or height) are limited

(Tunnel excavation can be divided into underground excavation and tunnelling

Dredging is the removal of soil from underwater

In mining, particularly considering the various equipments, excavation may be categorized as:

- Open-pit excavation (in surface mining)

- Underground excavation

- Tunnelling

- Underwater excavation

In open-pit excavation the various types of excavation methods, as mentioned in numbers 1

to 5 above, are used For underground operations, because of space and other limitations,

the type of the equipment that can be used are quite different from size, capacity and manoeuvrability points of view, as will be discussed later Special tunnelling machines are

employed in general tunnelling operations (which are usually different from ore mining operations) The environmental conditions for underwater excavations are quite different

from others, as the name implies; however, depending on each particular case some of the equipment for other types of excavation might be utilized for excavating under the water, or other special equipment would be necessary Tunnelling and underwater equipment are not discussed further in more detail in this study

2.2.1 Open-pit mining (surface mining) cyclic machines

Five different types of cyclical excavating machines can be identified; these are:

Figure 1 shows the schematics of these machines illustrating the basic difference between

their structures The power shovel is the most efficient of the various machines for excavating and loading large quantities of soil The dragline is the unit of excavating

equipment most ideally suited to handle loose bulk excavation It operates most efficiently from an elevation higher than the soil being dug, thus very suitable for original surface; it is seldom used for excavating at or above its travel level

Fig 1 More frequently used excavating machines

Unlike the power shovel none of its power is available for direct pressure on the soil The bucket is filled by pulling it toward the dragline after being penetrated into the soil only by the force of its weight The dragline performs many kinds of loose bulk excavation well; it has an extensive use in overburden stripping and surface mining Draglines are mounted on crawlers which enable them to work on tight areas

The scraper is designed for loading a thin layer of soil over a large area It has the advantage

of being able to haul and unload the soil to the desired destination Thus it is very appropriate for bulk wide-area excavation This machine is mostly pushed or/and pulled by tractors mounted on rubber tires; the cutting edge of the bowl (its bucket) penetrates 4-6 in into the soil, depending on the density of the soil formation Difficulty is encountered in loading loose dry sand and rock and, also, in unloading wet, sticky soil Their greatest use is found in unconsolidated soil that requires little or no loosening; but they are finding increasing applications in loading and hauling in open-pit mining

Robotic Excavation 277

The clamshell is most suitable for limited-area vertical excavation, like foundation

excavations; for this reason, most generally it is used as a secondary unit to muck out in the rear of the more productive machines For various jobs that call for removal of the soil from below the level where the machine rests, or require moving the soil above the machine, in particular where the soil being dug is loose, soft or wet, the clamshell is ideal The clamshell consists of a bucket hung from the boom of a crane that can be either crawler or wheel mounted The two halves of the bucket are dropped onto the soil to be excavated; then the bucket is closed, encompassing soil between the two halves

The backhoe is customarily a secondary tool in surface mining Contrary to the shovel and

dragline where the general concern is the volume excavation, the backhoe is convenient for scraping off and cleaning adhering overlay soil from surface, and also for trenching and digging ditches

2.2.2 Underground mining cyclic machines

The choice of equipment employed for underground mining primarily is enforced by the properties of the ore to be excavated The physical size of the ore and its geometry, that determine the method of mining, and the cost are secondary parameters For instance, continuous mining machines can be used for soft and semi hard soil, but do not have much success with hard rock that must be fragmented by blasting (or alternative method) before excavation

The machines for underground mining are much smaller in size and the capacity in comparison with the equipment for open-pit mining Two most used underground mine cyclic excavators are:

- Overshoot loader

- Load-Haul-Dump (LHD) unit

Overshoot Loader is a device which picks up the blasted soil from the front and without

turning discharges it to the rear in a truck to do the haulage, or to a conveyor It may be powered by compressed air, electricity or diesel engine The mounting can be crawlers, wheels or it is bound to move on rails The operator stands by the side of the machine, or he can operate from a few meters away by a remote system, if equipped Overshoot loaders are usually small in size to be able to work in small drifts

In larger mines a Loader (front-end loader) can be used to excavate and transfer the soil to a mining truck (dump-truck) A loader is extensively used in construction and road work,

and to a less extent in surface mining; in the same way it can be used for loading the ore However, the size of loader, and the space it requires for operation make it less desirable for underground, unless for the wide and high stopes, where the high mobility and rapid loading overweighs the shortcoming

A Load-Haul-Dump machine, or simply LHD, as the name implies (Figure 2), can combine

the work of a loader and a dump-truck In this way, one operator works instead of two in the former case LHD's are specially designed for working in mines; their physical structure, and size thus enable them to operate and move without difficulty in narrower areas and with smaller height Moreover, they are made in two parts hinged together in order to facilitate their turning through curves (Figure 3) LHD's are mounted on rubber tires which give them more mobility, and they are widely used in underground mining work Some LHD loaders are equipped with two buckets; in this way their transportation capacity is increased